The objective is to provide students, educators and researchers accurate, inexpensive and easily accessible visual data on human embryonic development. Aligned digital images of the serial sections of the best normal human embryos in the Carnegie collection will be made available on computer disks. The serial sections of at least one specimen from each of the 24 stages or sub-stages (stage 4 is missing) will be digitallyduplicated. It is anticipated that the databases at three stages will have been completed by the end of the second year of the initial grantleaving a balance of 21 stages. The period covered is the most critical time of prenatal development when all of the body systems are laid down and most serious malformations begin. The sections will be captured digitally at the site of the collection at 5 M pixel, 24 bit resolution and up to 40X magnification. The raw data will be sent via the Internet to the Pi's lab where the section images will be digitallyenhanced, contoured, aligned, labeled, high-resolution tiles assembled and each specimen's external surface 3D reconstructed. A page will be constructed for each section image totaling approximately 7,000. Each page will have a small 3D reconstruction showing the plane and level of the section image and multiple options, e.g., measuring bar, section numbers, labels, multiple zoom levels up to 1,OOOX magnification. The viewer will be able to select section images at any level in the embryo and rapidly scan them in alignment. The databases on the specimens will be replicated commercially and made available on CDs and DVDs (depending on user needs) at a nonprofit fee of no more than $10 to $20 each that covers handling,shipping and replacement. Users will be able to view the data on an imaging station that costs about $1200 and iscurrently available in many institutions. This project will make available for the first time the microscopic, sectional morphology of human embryos, which can be viewed in ones own facility and will enable students to learnhuman embryology from actual specimens and educators to produce many varied instructional media and provide a valuable reference for developmental biologists.